( B90 ) 



whicli some litres were collected, consist exciusi\ely of free nitrogen 

 and carbon dioxide; no trace of hydrogen, methane or niti'ons 

 oxide (NjO) was found. 



As regards the micro-organisms Avhich take part in tliis process, 

 a microscopical examination of the said bacterial mucus, which consists 

 of a finely granulated substance, shows the presence of very small 

 rod-like bacteria (fig. 1) and further there are found in the cultures 

 infusoria, amcebae, monads, spirillae, other small bacteria and vibrionae; 

 larger rod-bacteria or spore-forming organisms were not detecte(L 

 That the bacteria, involved in the i)rocess, are no sjjore forming 

 organisms, was also shown by the fact, that no pasteurised material 

 of whatever origin vn^'^l i'vom a ditch or from the soil) can cause 

 denitriiication in the presence of cellulose. 



Many experiments have been made with the object of isolating 

 the bacteria taking part in the denitrification, l»ut always with a 

 negative result. By inoculation on meat-gelatin and cultivating at 

 '24^ I several times obtained pure cultures i)ï BucUbis stutzeri Xkum. 

 and Lehm., which bacterium was also found in large numbers in 

 those cases where other denitrifying bacteria were present, so that 

 denitriiication with cellulose is a new accumulation experiment for this 

 important species, which, however, dops not attack the cellulose itself. 



On using meat-agar or one of the following culture liquids: 



Tapwater 100, agar 2, sodium lactate 2, KXO, 0,05, KJlPO, 0,05, 

 Tapwater 100, agar 2, glucose 2, KNO, 0,05, K,HPO, 0,05, 



and cultivating at 35^ other bacteria besides Ji. stiitzeri were found 

 and these were nearly always denitrifying ones. Very often a mucous 

 colonv of a motionless, non-spore forming denitrifying bacterium 

 became conspicuous, while in other cases a small, slightly denitrify i]ig 

 spirillum may be isolated. No permanent denitrification with paper 

 could, however, be obtained with any of these forms or with any 

 combination thereof, even the crude mixture as it is formed on the 

 plates was not capable to do tliLs. The fact, that these bacteria nun- 

 cause a temporary faint evolution of gas (which, at first, made me 

 suspect, that the destruction of cellulose could be accomplished by 

 ordinary denitrifying bacteria) must be attributed to the presence of 

 small quantities of impurities in the cellulose. Still, I think we may 

 take it for granted, that we are dealing here not with an anaerobic 

 but with an aerobic bacterium, first of all, because all known denitri- 

 fying bacteria are aerobic and only beha\ e anaërobically in the presence 

 of saltpetre, secondly because methylene-blue is not reduced, when 

 added to a medium in which cellulose is denitrifying, whilst in 



